1. Field of the Invention
The present invention relates to a mobile unit and a controller for a mobile unit, and specifically relates to a controller for correction control to accurately turn a self-controlled mobile unit.
2. Description of the Related Art
Robots (a type of mobile unit) which move within a defined region to accomplish work have been known for sometime. Such a robot works in predetermined wide and travels in the zigzag pattern shown in FIG. 13 to accomplish work completely within a region. In this zigzag pattern, the robot repeats a process of advancing a distance L, turning 90.degree., and advancing pitch p, and turning 90.degree. from a starting point to a goal.
In order to accurately pursue this zigzag pattern, the robot must accurately turn 90.degree.. When driving the wheels and measuring the amount of rotation of the wheels of the robot via an encoder, some slippage occurs between the wheels and the floor, such that the robot cannot turn with accuracy. Installing a gyroscopic sensor in a robot has been considered to measure the actual turning angle of the robot and correct the shifting (error) of the turning angle caused by slippage of the wheels. Typically, when the detection result of a gyroscopic sensor is fed back to accomplish correction in real time, turning cannot be accomplished rapidly due to the time required for detection by the gyroscopic sensor. Therefore, if the shifting of the turning angle is determined by a gyroscopic sensor after a predetermined rotation and controls are repeated to accomplish turning in accordance with said shifting, turning can be rapidly accomplished without requiring typical detection by the gyroscopic sensor.
The disadvantages described below arise when turning is corrected based on the detection result of a gyroscopic sensor.
1. First Disadvantage
Time is required to accomplish the aforesaid angle correction in the above-mentioned control method. For example, when the target turning angle is 90.degree., the robot continues reciprocal movement forward and back at the target turning angle (e.g., between 89.degree. and 91.degree.), in one type of oscillation state.
2. Second Disadvantage
Although slippage does not readily occur between the wheels and the floor when, for example, the floor is dry, slippage easily occurs when the floor is waxed. Since conventional correction methods are standardized, it has not been possible to achieve suitable correction in accordance with a given condition, such that correction is inadequate with regards to precision and work time.